Polo Players Edition

DEC 2018

Polo Players' Edition is the official publication of the U.S. Polo Association. Dedicated to the sport of polo, it features player profiles, game strategy, horse care, playing tips, polo club news and tournament results.

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16 POLO P L A Y E R S E D I T I O N E Q U I N E A T H L E T E BY HEATHER SMITH THOMAS STRESSED OUT S tress is a part of life—for horses or humans. Adversities challenge our minds and bodies and different individuals deal with it in different ways. Physical and mental stresses in small doses can make us stronger. Stress can be insignificant if temporary and short term. How the body reacts to stress (with production of cortisol and other hormones) can be helpful in the short term, helping the horse (or human) focus on the problem at hand. The horse stressed by fear of a predator can run faster, for instance. If he's stressed by a winter storm his body goes into survival mode and he can go without feed a bit longer, until the blizzard ends and he can go back to grazing again. If stress is prolonged, however, the very things that enable the body to endure the short-term adversity start to become detrimental instead of helpful. Cortisol production (a natural steroid) triggered by stress begins to hinder the immune system. Prolonged stress can lead to illness (opportunistic diseases take advantage of the depressed immunity), ulcers and other bad things. In nature, stresses for the horse were usually temporary. The herd sensed danger, became alarmed and fled, outrunning the predator, and then they relaxed and went back to grazing again. The wind-whipped rain or snow drove them to shelter behind a hill, out of the wind, lasted for part of a day and then subsided. Only a long-term stress like severe drought or a bad winter and subsequent starvation was truly detrimental. Our domesticated horses, however, have more to deal with than what Mother Nature throws at them, and stress can often be a negative factor in their lives. Sometimes the effects of stress are obvious (the horse gets "shipping fever" after a long transport, or a group of newly weaned foals—stressed by the weaning--get sick with influenza), but often the effects of stress are subtle; we may not always recognize them unless they result in poor performance, stereotypic behavior, or ulcers. There are many stressors in our horse's lives, and not all horses react the same way in how they deal with stress. Weather Stress Horses adapt to changes of season, growing longer, thicker hair for winter and putting on a layer of insulating fat under the skin. In summer they've shed out and grown shorter hair and the circulatory system adapts—bringing blood closer to the skin surface to help dissipate core body heat and help facilitate sweating. In natural conditions horses can usually handle the stress of cold weather, or summer's heat. When humans enter the picture, however, we often add to these stresses by how we use and manage our horses. We may haul horses from a warmer southern climate to a colder northern climate and they have trouble making a fast adjustment, not having had a chance to grow a winter hair coat. Horses moved from Florida or Texas to Minnesota or Wyoming may have a tough time that first winter (and be more vulnerable to illness). It may take a year before they fully adapt to the seasons in their home. The same is true for horses going from a colder climate to a warm one; they may suffer heat stress or lose the ability to sweat properly (anhidrosis). How we use our horses may also increase the effects of weather stress. If we keep horses blanketed in winter, or clip them so we don't have to dry a long winter coat after exercise and sweating, they may chill more readily. Likewise, if we use them hard in summer, they may suffer heat stress due to fatigue and dehydration. Transport Stress All horses are stressed by travel, especially if it involves a long time in transport, but some are stressed more than others. The circumstances of shipping may make a difference in the level of stress, and the physiological impact of that stress. Horses that are stressed too much are more likely to become ill. Multiple studies have shown that confining horses to a trailer for long periods of time has detrimental effects on the respiratory system. The longer the trip, the more likely the horse may end up with a variety of problems--infections like shipping fever or pleuritis, or impaction. Horses generally don't drink well when traveling. Many of them are too stressed, even though it might not be obvious that they are stressed, and won't relax enough to drink, or might not want to drink strange water at a rest stop, and thus dehydrate during travel. Some won't eat well during a long trip because they are stressed. Several studies have shown that transport in itself is a stressful event for horses. Two indicators of stress are a rise in heart rate and blood cortisol concentrations. The neutrophil- lymphocyte ratios change; there is usually a decrease in lymphocytes when horses are transported. These are the cells necessary for a good immune response. Carolyn Stull, PhD (University of Anything from work to weather can effect a horse's health

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